Golf ball

ABSTRACT

A matte colored golf ball which is free of luster and gloss has a good appearance in which injection marks that form during injection molding of a cover layer—be it an intermediate layer or an outermost layer—are difficult to see and scuffing on the cover surface is inconspicuous. The golf ball includes a core, an outermost layer, an intermediate layer therebetween, and a coat formed on the surface of the outermost layer. The intermediate layer is formed of a resin composition containing a thermoplastic resin and a colorant consisting of a fluorescent dye or a fluorescent pigment and has a specific visible light transmittance, the outermost layer is molded of a transparent or translucent resin composition that is free of fluorescent dye, and the coat is formed of a urethane-based coating composition containing delustering particles.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2019-121009 filed in Japan on Jun. 28, 2019, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a multi-piece solid golf ball having a core, an intermediate layer, an outermost layer and a coating layer.

BACKGROUND ART

The dimples formed on the surface of a golf ball are an important constituent element that increases the aerodynamic performance in the flight of the ball, and can also be a factor determining the aesthetic appearance and decorativeness of the ball. In colored golf balls in particular, the impression given by the ball appearance is collectively determined by a combination of, for example, the shapes of the dimples, the color of the ball and effect pigments. Many colored balls include fluorescent colorants and the like in the cover layer (outermost layer). There also exist golf balls having a coat obtained by including an effect pigment such as a polarizing pigment in a urethane or other coating resin.

Art relating to colored golf balls having a bright, diaphanous hue includes that disclosed in JP-A 2012-105725 and JP-A 2012-34776. Yet, although these golf balls are colored golf balls having a bright, diaphanous hue, such a ball appearance is readily subject to dimple-shaped shadows and light-reflecting effects, which adversely affects play.

In addition, so-called matte colored golf balls which have a colored appearance but are delustered or free of gloss to such a degree that dimple contours on the surface of the ball cannot be discerned have been popular recently.

However, conventional matte colored golf balls are obtained by including a delusterant such as silica primarily in the urethane or other resin coating material used to form the ball coat. Such golf balls have a matte appearance that looks as if there are no dimples, but injection marks such as gate marks which arise during injection molding of the outermost of the one or more cover layers that are formed can be seen through the coat. No consideration is given in such art to the formulation and light transmittance of the intermediate layer or outermost layer-forming cover material.

Moreover, because it is common in colored golf balls to include a light-harvesting dye in the resin material for the outermost layer of the cover and thereby make the outermost layer colored, one problem that arises is that, when numerous scuff marks form on the cover surface with prolonged use of the ball, such scuffing on the surface becomes conspicuous on account of the color, worsening the impression made by the ball's appearance.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a matte colored golf ball that is free of luster and gloss, which ball has a good appearance in that injection marks which form during injection molding of a cover layer such as an intermediate layer or outermost layer are not readily visible and scuffing on the cover surface is inconspicuous.

As a result of extensive investigations, we have made a discovery regarding a matte colored golf ball having a core, an outermost layer and an intermediate layer therebetween and having also, formed on a surface of the outermost layer, a coat composed of an inorganic filler-containing matte coating. Namely, we have found that by adding an inorganic filler such as a light-harvesting fluorescent dye to the intermediate layer-forming material and by also using in the outermost layer-forming material a resin material which contains no light-harvesting fluorescent dye and is transparent or translucent, thus combining the above intermediate layer having a visible light transmittance within a specific range and the above outermost layer, owing to the synergistic effects of these layers, there can be provided a golf ball on which, with no loss of fluorescent coloration or the matte effect, the injection marks that arise during injection molding of a cover layer—be it the intermediate layer or the outermost layer—become difficult to see, enabling the ball to fully exhibit the distinctive appearance that is desired.

Accordingly, the invention provides a golf ball having a core, an outermost layer, an intermediate layer between the core and the outermost layer and a coat formed on a surface of the outermost layer, wherein the intermediate layer is formed of a resin composition containing (A) a thermoplastic resin and (B) a colorant consisting of a fluorescent dye or a fluorescent pigment, a 2 mm thick sheet molded from the resin composition has a visible light transmittance with an average value at wavelengths in the 380 to 780 nm spectrum of from 2.0 to 70.0%, the outermost layer is molded of a transparent or translucent resin composition that is free of fluorescent dye, and the coat is formed of a urethane-based coating composition containing delustering particles.

In a preferred embodiment of the golf ball of the invention, the thermoplastic resin of component (A) includes either of the following components (a) and (b):

(a) an ethylene-α,β-unsaturated carboxylic acid copolymer or a metal salt thereof or both,

(b) an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer or a metal salt thereof or both.

In another preferred embodiment of the inventive golf ball, the content of component (B) is from 0.001 to 0.2 part by weight per 100 parts by weight of component (A).

In yet another preferred embodiment, the resin composition of the intermediate layer further includes (C) an inorganic filler or organic filler in an amount of from 0.01 to 1.0 part by weight per 100 parts by weight of component (A).

In still another preferred embodiment, a 2 mm thick sheet molded from the resin composition used in the intermediate layer has a visible light transmittance of from 3.0 to 60.0%.

In a further preferred embodiment, the resin composition used to form the outermost layer contains a polyurethane resin as the base resin.

In a yet further preferred embodiment, a 2 mm thick sheet molded from the resin composition used in the outermost layer has a visible light transmittance of from 4.0 to 50.0%.

In a still further preferred embodiment, the coat has on a surface thereof an average roughness Ra of from 0.5 to 1.0.

In another preferred embodiment, the delustering particles in the urethane-based coating composition used to form the coat are silica.

In yet another preferred embodiment, the silica serving as the delustering particles has an average primary particle size of from 1.0 to 3.0 μm and a BET specific surface area of from 200 to 400 m²/g.

Advantageous Effects of the Invention

The golf ball of the invention imparts an illusory effect whereby a golf ball which has dimples appears to be free of dimples and also is able to conceal injection marks that form during injection molding of a cover layer—be it the intermediate layer or the outermost layer, thereby exhibiting a good appearance with a matte color in which scuffing on the cover surface is inconspicuous.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The objects, features and advantages of the invention will become more apparent from the following detailed description.

The golf ball of the invention includes, from the inside: a core, an intermediate layer and an outermost layer.

The core may be formed using a known rubber material as the base. A known base rubber that is a natural rubber or a synthetic rubber may be used as the base rubber. More specifically, it is recommended that polybutadiene, especially cis-1,4-polybutadiene having a cis structure content of at least 40%, be chiefly used. If desired, natural rubber, polyisoprene rubber, styrene-butadiene rubber or the like may be used together with the foregoing polybutadiene in the base rubber. The polybutadiene may be synthesized with a titanium-based, cobalt-based, nickel-based or neodymium-based Ziegler catalyst or with a metal catalyst such as cobalt or nickel.

A co-crosslinking agent such as an unsaturated carboxylic acid or a metal salt thereof, an inorganic filler such as zinc oxide, barium sulfate or calcium carbonate, and an organic peroxide such as dicumyl peroxide or 1,1-bis(t-butylperoxy)cyclohexane may be included with the base rubber. Where necessary, a commercial antioxidant or the like may also be suitably added.

The core can be produced by vulcanizing/curing the rubber composition containing the above ingredients. For example, production may be carried out by kneading the composition using a mixer such as a Banbury mixer or a roll mill, compression molding or injection molding the kneaded composition using a core mold, and curing the molded body by suitably heating it at a temperature sufficient for the organic peroxide and the co-crosslinking agent to act, i.e., from about 100° C. to about 200° C., and preferably from 140 to 180° C., for a period of 10 to 40 minutes.

At least two cover layers are formed over the above core as core-encasing members. Of these cover layers, that positioned on the outermost side is the outermost layer. One or more intermediate layer is formed between this outermost layer and the core.

At least one intermediate layer is formed of a resin composition that includes (A) and (B) below:

(A) a thermoplastic resin, and

(B) a colorant consisting of a fluorescent dye or a fluorescent pigment. Components (A) and (B) are described below.

(A) Thermoplastic Resin

Exemplary thermoplastic resins include, without particular limitation, resins that have hitherto been used as golf ball materials, such as ionomeric resins, polyester resins, polyurethane resins, polyamide resins, polyolefin resins, olefin-based thermoplastic elastomers and styrene-based thermoplastic elastomers. Ionomeric resins are especially suitable and preferably include either of (a) and (b) below:

-   (a) an ethylene-α,β-unsaturated carboxylic acid copolymer and/or a     metal salt thereof, -   (b) an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated     carboxylic acid ester copolymer and/or a metal salt thereof.

Specific examples of the α,β-unsaturated carboxylic acid in components (a) and (b) include acrylic acid, methacrylic acid, maleic acid and fumaric acid. Acrylic acid and methacrylic acid are especially preferred. The α,β-unsaturated carboxylic acid ester in component (b) is preferably a lower alkyl ester of the above unsaturated carboxylic acid, specific examples of which include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate and butyl acrylate. Butyl acrylate (butyl n-acrylate, butyl i-acrylate) is especially preferred.

Metal ion neutralization products of the copolymers in components (a) and (b) can be obtained by partially neutralizing acid groups on the olefin-unsaturated carboxylic acid copolymer or the olefin-unsaturated carboxylic acid-unsaturated carboxylic acid ester copolymer with metal ions. Illustrative examples of metal ions which neutralize the acid groups include Na⁺, K⁺, Zn⁺⁺, Cu⁺⁺, Mg⁺⁺, Ca⁺⁺, Co⁺⁺, Ni⁺⁺ and Pb⁺⁺. Preferred use can be made of Na⁺, Li⁺, Zn⁺⁺, Mg⁺⁺ and Ca⁺⁺ in particular. Such neutralization products may be obtained by a known method. For example, a neutralization product may be obtained by using, for reaction with the above copolymer, a compound such as a formate, acetate, nitrate, carbonate, bicarbonate, oxide, hydroxide or alkoxide of the above metal ion.

Known substances may be used as components (a) and (b). Illustrative examples include commercial products such as the following acid copolymers: Nucrel® N1560, Nucrel® N1214, Nucrel® N1035, Nucrel® AN4221C, Nucrel® AN4311, Nucrel® AN4318 and Nucrel® AN4319 (all products of DuPont-Mitsui Polychemicals Co., Ltd.). Illustrative examples of metal ion neutralization products of acid copolymers include Himilan® 1554, Himilan® 1557, Himilan® 1601, Himilan® 1605, Himilan® 1706, Himilan® AM7311, Himilan® 1855, Himilan® 1856 and Himilan® AM7316 (all products of DuPont-Mitsui Polychemicals Co., Ltd.), and Surlyn® 7930, Surlyn® 6320, Surlyn® 8320, Surlyn® 9320 and Surlyn® 8120 (E.I. DuPont de Nemours and Company).

The overall amount of thermoplastic resin serving as component (A) is not particularly limited, although it is recommended that the thermoplastic resin be included in an amount which is typically at least 70 wt %, preferably at least 80 wt %, and more preferably at least 90 wt %, of the total amount of the resin composition. When enough is not included, the desired effects of the invention may not be achievable.

(B) Colorant Comprising Fluorescent Dye or Fluorescent Pigment

This invention is directed at a colored golf ball whose surface is free of luster and soft-toned. A colorant consisting of a fluorescent dye or a fluorescent pigment is included for this purpose as component (B) in the intermediate layer-forming resin material. Color is imparted to the intermediate layer by suitably including a known fluorescent dye or fluorescent pigment as the colorant. Examples include solvent yellow, solvent orange, anthraquinone and phthalocyanine (all of which are dyes), and also yellow fluorescent pigments, pink fluorescent pigments and orange fluorescent pigments. Known commercial products may be used as these colorants.

In this invention, of fluorescent colorants, the use of one that is light harvesting is preferred. Light-harvesting fluorescent colorants are materials which have the ability to collect sunlight and convert the wavelength to the long-wavelength side as fluorescent light. These materials are characterized in that they collect light by totally reflecting it at the interior of the colored material and guiding it to the dimple edges, where the light is emitted in a concentrated state, and they produce intense coloration.

Such light-harvesting fluorescent colorants include systems that generate orange, pink, red, yellow, blue or violet colors. Commercial products may be used in any of these chromogenic systems. Examples of light-harvesting fluorescent dyes that may be used include those available from BASF under the trade names Lumogen F Yellow 083, Lumogen F Orange 240, Lumogen F Red 305 and Lumogen F Blue 650, and those available from Kashinomoto Technologies Co., Ltd. under the trade names Lumicolor Red, Smart Color LP Green, Smart Color LP Yellow and Smart Color LP Orange.

The amount of component (B) included per 100 parts by weight of component (A) is from 0.001 to 0.2 part by weight, and preferably from 0.005 to 0.1 part by weight. When this amount is low, the fluorescence may weaken and the desired decorativeness may not be obtained. On the other hand, when this amount is high, migration of the colorants, especially dyes, may arise, staining objects that come into contact with the golf ball.

(C) Inorganic Filler or Organic Filler

The resin composition of components (A) and (B) may further include, as component (C), an inorganic filler or an organic filler. The purpose of including this inorganic or organic filler is, as subsequently described, to suitably prepare the resin composition so that it has the desired transmittance in the visible light spectrum. However, component (C) is not an essential ingredient in this invention.

In cases where component (C) is an inorganic filler, illustrative examples include, without particular limitation, zinc oxide, barium sulfate, calcium carbonate, titanium dioxide and silica. Adding an inorganic filler makes it possible to impart translucency and to adjust the color.

In cases where component (C) is an organic filler, illustrative examples include, without particular limitation, fine particles of crosslinked polymethyl methacrylate (crosslinked PMMA), crosslinked polybutyl methacrylate, crosslinked polyacrylate ester, crosslinked acrylic-styrene copolymer, melamine resin or polyurethane.

The amount of component (C) added per 100 parts by weight of component (A) is from 0.01 to 1.0 part by weight, and preferably from 0.02 to 0.2 part by weight. When too much is added, the hiding properties may become excessive, detracting from the decorativeness of a stylish ball, or the change in color when color fading occurs due to sunlight exposure may increase.

The resin composition can be obtained by mixing together the above ingredients using any of various types of mixers, such as a kneading-type single-screw or twin-screw extruder, a Banbury mixer or a kneader.

Various additives may be optionally included in the resin composition. For example, pigments, dispersants, antioxidants, light stabilizers, ultraviolet absorbers and lubricants may be suitably added.

The intermediate layer has a thickness which, although not particularly limited, is preferably at least 0.5 mm, and more preferably at least 0.7 mm, but preferably not more than 1.7 mm, and more preferably not more than 1.4 mm.

The intermediate layer has a hardness on the Shore D scale which, although not particularly limited, is preferably at least 30, and more preferably at least 40, but preferably not more than 75, more preferably not more than 70, and even more preferably not more than 65.

A 2 mm thick sheet molded from the above resin composition has a visible light transmittance with an average value at wavelengths in the 380 to 780 nm spectrum of from 2.0 to 70.0%, and preferably from 3.0 to 60%. This measured visible light transmittance refers specifically to the average of the values measured at 1 nm increments in the 380 to 780 nm spectrum using any of various types of UV-visible light spectrophotometers. To obtain a matte, gloss-free ball appearance, it is necessary to prepare a resin composition having a relatively strong fluorescent color and also some degree of transparency. As a guide for this, the measured value for the visible light transmittance of the intermediate layer is specified as being within the above range.

Next, the outermost layer is described.

The outermost layer has a material hardness on the Shore D scale which, although not particularly limited, is preferably from 25 to 57, more preferably from 27 to 55, and even more preferably from 29 to 53.

The outermost layer has a thickness which, although not particularly limited, is preferably from 0.3 to 1.5 mm, more preferably from 0.4 to 1.2 mm, and even more preferably from 0.5 to 1.0 mm.

The outermost layer material is not particularly limited. Various thermoplastic resin materials and thermoset materials may be suitably used for this purpose. In this invention, given that the resin material is one that is transparent or translucent, particularly from the standpoint of the controllability of the golf ball on approach shots and the scuff resistance of the ball, the use of a urethane resin is preferred.

In particular, a thermoplastic polyurethane elastomer can be used as the urethane resin. Specific examples include products available under the trade name PANDEX from DIC Covestro Polymer, Ltd., and products available under the trade name RESAMINE from Dainichiseika Color & Chemicals Mfg. Co., Ltd.

To achieve an outermost layer that is transparent or translucent, it is preferable to not include in the resin material for this layer a colorant that is a light-harvesting fluorescent dye.

The resin material of the outermost layer may be rendered into a colored resin layer. In such a case, various pigments may be suitably added to the above-described polyurethane resin or other base resin within a range that does not detract from the advantageous effects of the invention.

The visible light transmittance of a 2 mm thick sheet molded from the resin composition used in the outermost layer is preferably from 4.0 to 50.0%, and more preferably from 10.0 to 40.0%. By thus forming an outermost layer having a relatively low transmittance, this layer acts in concert with the intermediate layer material to impart an illusory effect which makes it appear as if there are no dimples and also enables injection marks that form during injection molding to be fully concealed. Here, “translucent” is defined as having a transmittance of 3.0 to 10.0%, and “transparent” is defined as having a transmittance of more than 10.0%.

Golf balls in which the above-described core, intermediate layer and outermost layer are formed as successive layers can be manufactured by a customary method such as a known injection molding process. For example, a multi-piece golf ball can be obtained by placing, as the core, a vulcanized/molded material composed primarily of rubber within a specific injection mold and injecting an intermediate layer material over the core so as to obtain an intermediate sphere, and subsequently placing the intermediate sphere within another injection mold and injecting an outermost layer-forming material over the sphere. Alternatively, an outermost layer may be added via a method that encases the intermediate sphere with the outermost layer, such as by enveloping the intermediate sphere within two half-cups that have been pre-molded into hemispherical shapes and then molding under applied heat and pressure.

A plurality of dimples of one or more types may be formed on the surface of the outermost layer. Characteristics of the dimples such as their shape, diameter, depth, number and surface coverage are suitably selected.

The golf ball of the invention has a coat which is formed of a coating composition that contains delustering particles.

The coating composition is not particularly limited, although the use of a urethane-based coating is preferred. Given the need to be capable of enduring the harsh conditions of golf ball use, a two-part curable urethane coating is preferred, with the use of a non-yellowing urethane coating being especially preferred.

In the case of a two-part curable urethane coating, it is preferable to use as the base resin any of various polyols, such as saturated polyester polyols, acrylic polyols and polycarbonate polyols, and to use also, as the isocyanate curing agent, a non-yellowing polyisocyanate, examples of which include hexamethylene diisocyanate, isophorone diisocyanate, and adducts, biurets, isocyanurates, or mixtures thereof, of hydrogenated xylylene diisocyanate.

The delustering particles are exemplified by silica particles, melamine particles and acrylic particles. Specific examples include silica particles, polymethyl methacrylate particles, polybutyl methacrylate particles, polystyrene particles and polybutyl acrylate particles. Either organic particles or inorganic particles may be used, with the use of silica particles being especially preferred.

In terms of the light-quenching properties and ease of coating application, the delustering particles have a specific surface area, expressed as the BET specific surface area, which is preferably from 200 to 400 m²/g, and more preferably from 250 to 350 m²/g.

In terms of the ball spin performance and the light-quenching properties, the delustering particles have an average primary particle size which is preferably from 1.0 to 3.0 μm, and more preferably from 2.0 to 2.8 μm. When this value is more than 3.0 μm, the ball surface becomes rough, which may have an adverse effect on the spin performance, lowering this performance. On the other hand, when this value is too small, the light-quenching effect may diminish.

The content of delustering particles may be set to preferably from 5 to 10 parts by weight per 100 parts by weight of the base resin (combined amount of resin ingredients and solvent) in the coating composition for the coat. When this content is too high, the viscosity of the coating composition rises and the ease of coating application may worsen; when it is too low, the light-quenching effect may diminish.

From the standpoint of both the spin rate of the ball on approach shots and the light-quenching properties, the surface of the coat has an average roughness Ra which is preferably from 0.5 to 1.0. The surface roughness Ra of the coat refers herein to the arithmetic mean roughness obtained in accordance with JIS B 0601 (1994).

The reflectance of the coat, as measured with a glossimeter, is preferably 5.0 or less at an incident angle of 20°, 20.0 or less at an incident angle of 60° and 40.0 or less at an incident angle of 85°. With a coat normalized in such a way that the above reflectances satisfy these numerical ranges, a delustering effect can be imparted. Measurement of the reflectance with a glossimeter was carried out with the instrument described in the examples below and using an ABS resin plate to which a 20 μm thick coat had been applied.

Ball specifications such as the ball weight and diameter may be suitably set in accordance with the Rules of Golf.

EXAMPLES

The following Examples and Comparative Examples are provided to illustrate the invention, and are not intended to limit the scope thereof.

Examples 1 to 15, Comparative Examples 1 to 20

As shown in Table 1, the solid core in each example was produced by using the following rubber composition, which is common to all the examples, and vulcanizing for 15 minutes at 155° C.

TABLE 1 Rubber composition for core A (common to (parts by weight) all Examples) Polybutadiene 100 Barium sulfate 26.6 Zinc oxide 4 Zinc stearate 3 2,2-Methylenebis(4-methyl-6-tert-butylphenol) 0.1 Zinc salt of pentachlorothiophenol 0.6 Zinc acrylate 23.5 Dicumyl peroxide 0.3 1,1-Di(tert-butylperoxy)cyclohexane 0.3

Details on the above core materials are given below.

-   Polybutadiene: Available under the trade name “BR01” from JSR     Corporation -   Barium sulfate: Available from Sakai Chemical Co., Ltd. -   Zinc oxide: Available from Sakai Chemical Co., Ltd. -   Zinc stearate: Available from NOF Corporation -   2,2-Methylenebis(4-methyl-6-tert-butylphenol):     -   An antioxidant available under the trade name “Nocrac NS-6” from         Ouchi Shinko Chemical Industry Co., Ltd. -   Zinc acrylate: Available from Nippon Shokubai Co., Ltd. -   Dicumyl peroxide: An organic peroxide available under the trade name     “Percumyl D” from NOF Corporation -   1,1-Di(tert-butylperoxy)cyclohexane:     -   An organic peroxide available under the trade name “Perhexa         C-40” from NOF Corporation

Formation of Cover Layers (Intermediate Layer and Outermost Layer)

Next, intermediate layer-encased spheres having a diameter of 41.05 mm were produced by injection molding the intermediate layer-forming resin materials shown in Table 2 below to a thickness of 1.2 mm over the 38.65 mm diameter cores obtained as described above.

TABLE 2 Intermediate layer material (pbw) B C D E F G H I J K (A) Himilan 1605 50 50 50 50 50 50 50 50 50 50 Himilan 1557 15 15 15 15 15 15 15 15 15 15 Himilan 1706 35 35 35 35 35 35 35 35 35 35 (B) Light-harvesting fluorescent dye (1) 0.060 Light-harvesting fluorescent dye (2) 0.060 Light-harvesting fluorescent dye (3) 0.012 0.031 0.010 0.065 0.017 0.026 0.012 Fluorescent dye 0.072 (C) Inorganic filler (titanium dioxide) 0.038 0.025 0.035 0.044 0.160 0.073 Others Fluorescent brightener 0.093 Magnesium stearate 0.9 0.9 0.8 0.9 0.2 0.9 0.4 0.2 Lubricant 0.03 Transmittance of resin material (%) 4.7 15.3 7.2 35.0 3.5 45.9 50.3 0.4 1.5 81.6

Details on the materials in the above table are given below.

-   Himilan 1605: An ionomeric resin available from Dow-Mitsui     Polychemicals Co., Ltd. -   Himilan 1557: An ionomeric resin available from Dow-Mitsui     Polychemicals Co., Ltd. -   Himilan 1706: An ionomeric resin available from Dow-Mitsui     Polychemicals Co., Ltd. -   Light-harvesting fluorescent dye (1):     -   Available under the trade name “Smart Color LP Yellow” from         Kashinomoto Technologies Co., Ltd. -   Light-harvesting fluorescent dye (2):     -   Available under the trade name “Smart Color LP Pink” from         Kashinomoto Technologies Co., Ltd. -   Light-harvesting fluorescent dye (3):     -   Available under the trade name “Lumicolor Red” from Kashinomoto         Technologies Co., Ltd. -   Fluorescent dye: Available under the trade name “Sumiplast Yellow     FL7G” from Sumika Chemtex Co., Ltd. -   Fluorescent brightener:     -   Available under the trade name “Hakkol PY1800” from Showa         Chemical Industry Co., Ltd. -   Lubricant: Available under the trade name “Sanwax 161-P” from Sanyo     Chemical Industries, Ltd.

Next, the outermost layer-forming material shown in Table 3 below was injection-molded over the above intermediate layer-encased sphere to a thickness of 0.8 mm, thereby producing a three-piece golf ball having a diameter of 42.7 mm. At this time, dimples common to all the examples were formed on the surface of the outermost layer in each Example and Comparative Example.

TABLE 3 Intermediate layer material (pbw) L M N O P Q (A) Thermoplastic urethane resin 100 100 100 100 100 Himilan 1605 50 Himilan 1557 15 Himilan 1706 35 (B) Light-harvesting fluorescent dye (1) 0.03 0.15 (C) Inorganic filler (titanium dioxide) 0.025 0.050 Transparent, translucent or opaque? transparent translucent opaque transparent opaque transparent Colored or colorless? colorless colorless colorless colored colored colorless Transmittance of resin material (%) 18.7 4.6 0.8 25.5 2.3 81.6

The details on the materials in Table 3 are the same as above. The thermoplastic urethane resin is an ether-type thermoplastic polyurethane (Shore D hardness, 35) available under the trade name PANDEX from DIC Covestro Polymer, Ltd.

The transparency (transparent/translucent/opaque) of the resin composition was adjusted by suitably adjusting the content of the titanium dioxide serving as component (C).

Next, using the two-part curable urethane coating made of a base resin and a curing agent shown in Table 4 below, the surface of the outermost layer was coated to a thickness of 15 μm.

TABLE 4 Resin composition of coating (pbw) R Base resin Saturated polyester polyol (molecular weight, 28,000) 27.5 Delustering particles (silica) 9 Solvent 72.5 Curing HDI isocyanurate (low-molecular weight) 42 agent Solvent 58

Details on the base resin and curing agent are given in (i) to (iv) below.

-   (i) First, a reactor equipped with a reflux condenser, a dropping     funnel, a gas inlet and a thermometer was charged with 140 parts by     weight of trimethylolpropane, 95 parts by weight of ethylene glycol,     157 parts by weight of adipic acid and 58 parts by weight of     1,4-cyclohexanedimethanol, following which the temperature was     raised to between 200 and 240° C. under stirring and the reaction     was effected by 5 hours of heating. This yielded a saturated     polyester polyol having an acid value of 4, a hydroxyl value of 170     and a weight-average molecular weight (Mw) of 28,000. -   (ii) Next, the polyester polyol synthesized above was dissolved in     butyl acetate, thereby preparing a varnish having a nonvolatiles     content of 70 wt %. -   (iii) The base resin was prepared by dissolving 27.5 parts by weight     of the saturated polyester polyol solution in butyl acetate (the     nonvolatiles content of this solution was 27.5 wt %), and mixing in     silica (“Finesil X-35” available from Maruo Calcium Co., Ltd.;     average primary particle size, 2.4 μm; BET specific surface area,     262 m²/g) as the delustering particles. -   (iv) Next, the isocyanate shown in Table 4 was dissolved in an     organic solvent and used as the curing agent. That is, HDI     isocyanurate (available as Duranate™ TPA-100 from Asahi Kasei     Corporation; NCO content, 23.1 wt %; nonvolatiles content, 100 wt %)     and, as the organic solvents, ethyl acetate and butyl acetate were     added in the proportions shown in Table 4, thereby preparing a resin     composition for use as a coating.

Table 5 shows the materials in the various layers of the golf balls obtained in the respective Examples and Comparative Examples, and also the diameters, compressive deformations and other properties of the balls. The transmittances of the intermediate layer and the outermost layer and the arithmetic mean roughness (Ra) of the coat are also shown in the same table. In addition, four appearance evaluations were carried out by the methods described below on the golf balls obtained in the Examples and the Comparative Examples. Those results too are presented in Tables 5 to 7.

Compression Deflection

The core, intermediate layer-encased sphere or ball was placed on a steel plate and the amount of deflection by each when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) was measured. In each case, the amount of deflection was a measured value obtained after temperature conditioning at 23.9° C.

Transmittances of Intermediate Layer and Outermost Layer

The intermediate layer-forming resin composition or outermost layer-forming resin composition was molded into a 2 mm sheet and, with this as the sample, the visible light transmittance was determined using the UV-1800 ultraviolet-visible spectrophotometer from Shimadzu Corporation. Tables 5 to 7 show the average values of measurements taken at 1 nm intervals in the 380 to 780 nm spectrum.

Appearance 1

The visibility of the dimples on the golf balls obtained in each example was visually evaluated and numerically rated according to the criteria shown below. The resulting scores are shown in Tables 5 to 7. A higher score indicates a better result. Scores of 2 or less were regarded as unacceptable.

Rating Criteria

-   -   4 points: Dimple edges indicating the dimple contours are         substantially invisible. Vertical intervals between base and         edge of individual dimples are substantially invisible.     -   3 points: Dimple edges indicating the dimple contours are         blurred but visible. Vertical intervals between base and edge of         individual dimples are blurred but visible.     -   2 points: Dimple edges indicating the dimple contours are         somewhat distinctly visible. Vertical intervals between base and         edge of individual dimples are somewhat distinctly visible.     -   1 point: Dimple edges indicating the dimple contours are         distinctly visible. Vertical intervals between base and edge of         individual dimples are distinctly visible.

Appearance 2

The visibility of injection marks that form in gate areas on the outermost layer (gate marks) during injection molding of the outermost layer was rated according to the criteria shown below. A higher score indicates a better result. Scores of 1 were regarded as unacceptable.

Rating Criteria

-   -   4 points: No visible injection marks.     -   3 points: Injection marks with inside diameters of about 3 mm         are visible.     -   2 points: Injection marks with inside diameters of about 5 mm         are visible.     -   1 point: Injection marks with inside diameters of about 10 mm         are visible.

Appearance 3

The fluorescent effect of the ball appearance was rated according to the criteria shown below. A higher score indicates a better result. Scores of 2 or less were regarded as unacceptable.

Rating Criteria

-   -   4 points: Fluorescent coloration is fully perceivable.     -   3 points: Fluorescent coloration is perceivable.     -   2 points: Fluorescent coloration is only slightly perceivable.     -   1 point: Fluorescent coloration is not perceivable.

Appearance 4

The balls were held isothermally at 23° C. and, using as the club a sand wedge mounted on a swing robot, each ball was struck five times at a head speed of 33 m/s and damage such as scuffing of the ball from the impact was visually rated according to the following criteria.

Rating Criteria

-   -   4 points: Substantially no visible scuffing.     -   3 points: Little visible scuffing.     -   2 points: Scuffing is somewhat clearly visible.     -   1 point: Scuffing is clearly visible.

TABLE 5 Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Core Material A A A A A A A A A A A A A A Diameter (mm) 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 Weight (g) 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 Compression deflection (mm) 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 Intermediate Material B B C C D D E E F F G G H H layer Diameter (mm) 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 Weight (g) 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 Compression deflection (mm) 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 Outermost Material L M L M L M L M L M L M L M layer Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Weight (g) 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 Compression deflection (mm) 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 Coat Material R R R R R R R R R R R R R R Thickness (μm) 15 15 15 15 15 15 15 15 15 15 15 15 15 15 Arithmetic mean roughness Ra 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 Intermediate layer transmittance 4.7 4.7 15.3 15.3 7.2 7.2 35.0 35.0 3.5 3.5 45.9 45.9 50.3 50.3 (380 to 780 nm) Outermost layer transmittance 18.7 4.6 18.7 4.6 18.7 4.6 18.7 4.6 18.7 4.6 18.7 4.6 18.7 4.6 (380 to 780 nm) Appearance 1 Dimple visibility 4 3 4 3 4 3 4 4 4 3 4 4 4 4 (visual) Appearance 2 Visibility of injection 4 4 4 4 4 4 4 4 4 4 4 4 3 4 marks formed during molding of outermost layer Appearance 3 Fluorescent effect 4 4 4 4 4 4 3 4 4 4 4 4 3 4 (visual) Appearance 4 Visibility of scuffing 4 4 4 4 4 4 3 3 4 4 3 3 3 3 (visual assessment of outermost layer from above)

TABLE 6 Comparative Example 1 2 3 4 5 6 7 8 9 10 Core Material A A A A A A A A A A Diameter (mm) 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 Weight (g) 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 Compression deflection (mm) 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 Intermediate Material B C D E F G H I I I layer Diameter (mm) 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 Weight (g) 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 Compression deflection (mm) 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 Outermost Material N N N N N N N L M N layer Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Weight (g) 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 Compression deflection (mm) 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 Coat Material R R R R R R R R R R Thickness (μm) 15 15 15 15 15 15 15 15 15 15 Arithmetic mean roughness Ra 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 Intermediate layer transmittance 4.7 15.3 7.2 35.0 3.5 45.9 50.3 0.4 0.4 0.4 (380 to 780 nm) Outermost layer transmittance 0.8 0.8 0.8 0.8 0.8 0.8 0.8 18.7 4.6 0.8 (380 to 780 nm) Appearance 1 Dimple visibility 1 1 1 1 1 1 1 4 3 1 (visual) Appearance 2 Visibility of injection 4 4 4 4 4 4 4 4 4 4 marks formed during molding of outermost layer Appearance 3 Fluorescent effect 1 1 1 1 1 1 1 1 1 1 (visual) Appearance 4 Visibility of scuffing 4 4 4 4 4 4 4 4 3 4 (visual assessment of outermost layer from above)

TABLE 7 Comparative Example Example 11 12 13 14 15 16 17 18 19 20 15 Core Material A A A A A A A A A A A Diameter (mm) 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 38.65 Weight (g) 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 35.1 Compression deflection (mm) 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 2.95 Intermediate Material J J J K K K K K G G G layer Diameter (mm) 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 41.05 Weight (g) 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 40.7 Compression deflection (mm) 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 2.65 Outermost Material L M N L M N O P O P Q layer Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Weight (g) 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 45.5 Compression deflection (mm) 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 2.40 Coat Material R R R R R R R R R R R Thickness (μm) 15 15 15 15 15 15 15 15 15 15 15 Arithmetic mean roughness Ra 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 Intermediate layer transmittance 1.5 1.5 1.5 81.6 81.6 81.6 81.6 81.6 45.9 45.9 45.9 (380 to 780 nm) Outermost layer transmittance 18.7 4.6 0.8 18.7 4.6 0.8 25.5 2.3 25.5 2.3 81.6 (380 to 780 nm) Appearance 1 Dimple visibility 4 3 1 4 3 1 4 3 4 3 4 (visual) Appearance 2 Visibility of injection 4 4 4 3 3 4 3 4 3 4 2 marks formed during molding of outermost layer Appearance 3 Fluorescent effect 2 2 1 1 1 1 3 4 3 3 3 (visual) Appearance 4 Visibility of scuffing 3 3 4 2 2 1 2 1 2 1 4 (visual assessment of outermost layer from above)

The results in Tables 5, 6 and 7 show that all of the golf balls obtained in Examples 1 to 15 according to the invention had a good overall ball appearance; that is, the balls had a matte look that made it seem as if there were no dimples and the injection marks that form during molding of the outermost layer also were invisible.

By contrast, in Comparative Example 1, the outermost layer of the ball had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 2, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 3, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 4, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 5, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 6, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 7, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 8, the intermediate layer had a low transmittance. As a result, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 9, the intermediate layer had a low transmittance. As a result, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 10, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 11, the intermediate layer had a low transmittance. As a result, there was little fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 12, the intermediate layer had a low transmittance. As a result, there was little fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 13, the outermost layer had a low transmittance. As a result, the dimple lands and boundaries were distinctly visible, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 14, the intermediate layer had a high transmittance. As a result, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 15, the intermediate layer had a high transmittance. As a result, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 16, the intermediate layer had a high transmittance. As a result, there was no fluorescent coloration and the finished golf ball was not a matte colored ball.

In Comparative Example 17, a fluorescent dye was used in the resin material of the outermost layer. As a result, scuffing was somewhat visible.

In Comparative Example 18, a fluorescent dye was used in the resin material of the outermost layer. As a result, scuffing was visible.

In Comparative Example 19, a fluorescent dye was used in the resin material of the outermost layer. As a result, scuffing was somewhat visible.

In Comparative Example 20, a fluorescent dye was used in the resin material of the outermost layer. As a result, scuffing was visible.

Japanese Patent Application No. 2019-121009 is incorporated herein by reference.

Although some preferred embodiments have been described, many modifications and variations may be made thereto in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without departing from the scope of the appended claims. 

1. A golf ball comprising a core, an outermost layer, an intermediate layer between the core and the outermost layer and a coat formed on a surface of the outermost layer, wherein the intermediate layer is formed of a resin composition containing (A) a thermoplastic resin, and (B) a colorant consisting of a fluorescent dye or a fluorescent pigment, a 2 mm thick sheet molded from the resin composition has a visible light transmittance with an average value at wavelengths in the 380 to 780 nm spectrum of from 2.0 to 70.0%, the outermost layer is molded of a transparent or translucent resin composition that is free of fluorescent dye, and the coat is formed of a urethane-based coating composition containing delustering particles.
 2. The golf ball of claim 1, wherein the thermoplastic resin of component (A) includes either of the following components (a) and (b): (a) an ethylene-α,β-unsaturated carboxylic acid copolymer or a metal salt thereof or both, (b) an ethylene-α,β-unsaturated carboxylic acid-α,β-unsaturated carboxylic acid ester copolymer or a metal salt thereof or both.
 3. The golf ball of claim 1, wherein the content of component (B) is from 0.001 to 0.2 part by weight per 100 parts by weight of component (A).
 4. The golf ball of claim 1, wherein the resin composition of the intermediate layer further comprises: (C) an inorganic filler or organic filler in an amount of from 0.01 to 1.0 part by weight per 100 parts by weight of component (A).
 5. The golf ball of claim 1, wherein a 2 mm thick sheet molded from the resin composition used in the intermediate layer has a visible light transmittance of from 3.0 to 60.0%.
 6. The golf ball of claim 1, wherein the resin composition used to form the outermost layer contains a polyurethane resin as the base resin.
 7. The golf ball of claim 1, wherein a 2 mm thick sheet molded from the resin composition used in the outermost layer has a visible light transmittance of from 4.0 to 50.0%.
 8. The golf ball of claim 1, wherein the coat has on a surface thereof an average roughness Ra of from 0.5 to 1.0.
 9. The golf ball of claim 1, wherein the delustering particles in the urethane-based coating composition used to form the coat are silica.
 10. The golf ball of claim 1, wherein the silica serving as the delustering particles has an average primary particle size of from 1.0 to 3.0 μm and a BET specific surface area of from 200 to 400 m²/g. 